There is provided a method of forming a layer, comprising depositing a seed layer on the substrate and depositing a bulk layer on the seed layer. Depositing the seed layer comprises supplying a first precursor comprising metal and halogen atoms to the substrate; and supplying a first reactant to the substrate. Depositing the bulk layer comprises supplying a second precursor comprising metal and halogen atoms to the seed layer and supplying a second reactant to the seed layer.